This invention relates generally to centrifugal blowers or fans and, more particularly, to a multiple outlet centrifugal blower for an electric drive motor for a mine truck.
Centrifugal blowers, ventilators, fans, pumps, and similar devices are designed to move quantities of air by raising the pressure of the air and discharging it at a desired volumetric flow rate through a pipe or duct. An apparatus requiring cooling, ventilation, or pressurization is often positioned at the discharge port of the pipe or duct. In order for the air to move at a continuous volumetric flow rate through the discharge port to cool, ventilate, or pressurize the apparatus, the air must be supplied with sufficient energy to overcome the downstream backpressure at the outlet. This backpressure is the sum of the pressure drop in the downstream system caused by the resistance of the air to move through the duct and the total air pressure at the discharge port. Oftentimes the downstream system has at least two separate branches through which air must be delivered to a corresponding number of apparatus that require cooling, ventilation, or pressurization. These systems typically comprise centrifugal blowers having two or more separate impellers wherein each impeller supplies air at a volumetric flow rate specific to an apparatus connected to its respective discharge port.
Such systems are typically incorporated into electric drive mine trucks. Other applications include, but are not limited to, various other earth-moving devices, railroad locomotives, and marine vessels. AC drive motors are located inside the rear wheels of such trucks. Power from these drive motors is transferred through a double reduction gear set to the rear wheels and tires to drive the truck. During operation of AC motors of this type to drive large trucks, significant amounts of heat are generated. To combat the generated heat, a second AC drive motor and an auxiliary inverter are incorporated into the structure of the truck and are used to power two independent impellers situated on a single double-ended blower unit. Air moved by the first impeller is ducted to the rear of the truck where it is used to cool the AC drive motors located inside the rear wheels of the truck, while air moved by the second impeller is ducted to the deck of the truck and used to power components of a control group associated with the motor. Such a dual-impeller ventilation system offers the benefit of control of the auxiliary blower speed independent of the engine speed of the truck.
The configuration of such a system, however, is mechanically complex, and the efficiency of the system is often sacrificed as the degree of complexity becomes greater. For example, many systems of the prior art that utilize a second AC drive motor to power a double-ended blower unit also incorporate a clutch device to modulate the amount of power that must be drawn from the power plant. Such devices have fans that often require up to 30 horsepower to rotate when they are engaged, thereby reducing the efficiency of the power plant and the overall fuel economy of the vehicle.
Increasingly complex mechanical systems tend to require an increasing number of parts, for which the amount of maintenance also increases. Blowers having fans that are in constant rotation are especially prone to increased maintenance due to the number of moving parts such as belts, bearings, and the like that are incorporated therein. As the amount of maintenance increases, the overall costs to service the system increases. Because the operation of a mine truck requires a crew of highly trained operators, electricians, and mechanics, the operation is an expensive proposition to begin with. Maintaining the blower and duct work of a separate ventilation system may become cost prohibitive as the complexity and degree of unreliability of the system increases.
What is needed in the art is a ventilation system that eliminates the second AC drive motor that powers the two impellers on the double-ended blower unit.
A ventilation system utilizing a centrifugal blower having an impeller directly couplable to a drive motor is disclosed herein. The system may be installed on a variety of vehicles and heavy duty equipment to work in conjunction with the power plants thereof to cool, ventilate, or pressurize both the components of the control groups as well as AC drive motors and other equipment.
The blower is a multiple outlet blower having a single impeller that provides both radial and axial airflows that are independent of each other. An obstruction in the path of one of the airflows does not substantially affect the other airflow. The blower typically includes a housing having an inlet port, first and second outlet ducts, and an impeller rotatably positioned and supported within the housing. The first outlet duct is configured to receive airflow in a radial direction with respect to blades arranged on the impeller, while the second outlet duct is configured to receive airflow in an axial direction with respect to the same blades.
An inlet chamber is preferably fixedly connected to the housing. The inlet chamber is configured to receive air through an opening therein and channel air to the inlet port. The inlet chamber is typically formed of front and back walls connected by at least one sidewall. The back walls contain openings therein to allow air to enter the inlet port.
First and second outlet ducts are disposed proximate an outer edge of the housing. The first outlet duct includes a throat portion dimensioned so as to have a width that is substantially equal to the width of an impeller blade. The throat portion has a tapered surface to define the throat portion as being narrower at a point proximate the tips of the impeller blades and wider at a point proximate the outer edge of the housing. The second outlet duct is configured to extend laterally away from a plane of the impeller, and is preferably positioned diametrically opposite the first outlet duct. Both outlet ducts have access covers removably positioned thereover to allow for the maintenance of the blower without requiring disassembly of the housing.